Tunable, thiol-ene, interpenetrating network hydrogels of norbornene-modified carboxymethyl cellulose and cellulose nanofibrils

Tessali X Morrison; William M Gramlich

doi:10.1016/j.carbpol.2023.121173

Tunable, thiol-ene, interpenetrating network hydrogels of norbornene-modified carboxymethyl cellulose and cellulose nanofibrils

Carbohydr Polym. 2023 Nov 1:319:121173. doi: 10.1016/j.carbpol.2023.121173. Epub 2023 Jul 1.

Authors

Tessali X Morrison¹, William M Gramlich²

Affiliations

¹ Department of Chemistry, University of Maine, Orono, ME 04469, USA.
² Department of Chemistry, University of Maine, Orono, ME 04469, USA; Advanced Structures and Composites Center, University of Maine, Orono, ME 04469, USA; Institute of Medicine, University of Maine, Orono, ME 04469, USA. Electronic address: william.gramlich@maine.edu.

PMID: 37567714
DOI: 10.1016/j.carbpol.2023.121173

Abstract

Carboxymethyl cellulose modified with norbornene groups (NorCMC) and cellulose nanofibrils (CNFs) produced through mechanical refining without chemical pretreatment formed interpenetrating network hydrogels through a UV-light initiated thiol-ene reaction. The molar ratio of thiols in crosslinkers to norbornene groups off the NorCMC (T:N), total polymer weight percent in the hydrogel, and weight percent of CNFs of the total polymer content of the hydrogels were varied to control hydrogel properties. This method enabled orders of magnitude changes to behavior. Swelling in aqueous environments could be significant (>150 %) without CNFs to minimal (<15 %) with the use of 50 % CNFs. NorCMC and CNF networks interacted synergistically to create hydrogels with compression modulus values spanning 1 to 150 kPa - the values of most biological tissues. T:N and total polymer weight percent could be varied to create hydrogels with different CNF content, but the same compression modulus, targeting 10 and 100 kPa hydrogels and providing a system that can independently vary fibrillar content and bulk modulus. Analysis of the effective crosslinks, thiol-ene network mesh size, and burst release of the polymer indicated synergistic interactions of the NorCMC thiol-ene and CNFs networks. These interactions enhanced modulus and degradation control of the network under physiological conditions.

Keywords: Carboxymethyl cellulose; Cellulose nanofibrils; Interpenetrating network hydrogels; Thiol-ene click chemistry.